The present disclosure generally relates to downhole fluid flow control and, more particularly, to flow distribution assemblies used to distribute fluid flow into surrounding subterranean formations.
In the course of completing wellbores that traverse hydrocarbon-bearing portions of subterranean formations, it is oftentimes desirable to inject various types of fluids into the wellbore for a number of purposes. For example, steam is often injected into surrounding formations to stimulate the production of high-viscosity hydrocarbons, and treatment fluids, such as hydrochloric acid, are often injected into a wellbore to react with acid-soluble materials present within the formation and thereby enlarge pore spaces in the formation. In other applications, water or a gas may be injected into the surrounding formations to maintain formation pressures so that a producing well can continue production. In yet other applications, a gravel slurry is deposited in spaced intervals surrounding well screens during gravel-packing operations.
Such fluid injection operations are typically carried out by placing an injection string at a desired location within a wellbore. The injection string oftentimes includes a wellbore screen assembly that includes one or more sand screens arranged about perforated production tubing. The annulus between the sand screens and the wellbore wall is generally gravel-packed to mitigate the influx of formation sands derived from the surrounding subterranean formations. Packers are customarily set above and below sand screen assemblies to seal off the annulus in the zone where production fluids flow into the production tubing. The annulus around the sand screens is then packed with a gravel slurry, which comprises relatively coarse sand or gravel suspended within water or a gel and acts as a filter to reduce the amount of fine formation sand reaching the screens.
During the gravel packing process, annular sand “bridges” can form around the sand screen assembly that may prevent the complete circumscribing of the screen structure with gravel in the completed well. This incomplete screen structure coverage by the gravel may leave an axial portion of the sand screen exposed to the fine formation sand, thereby undesirably lowering the overall filtering efficiency of the sand screen structure.
One approach to overcoming annulus sand bridges has been to incorporate shunt tubes that longitudinally extend across the sand screens. The shunt tubes provide a flow path that allows the inflowing gravel slurry to bypass any sand bridges that may be formed and otherwise permit the gravel slurry to enter the annulus between the sand screens and the wellbore beneath sand bridges, thereby forming the desired gravel pack beneath it.